#include<bits/stdc++.h>
using namespace std;
int N,M;
long long arr[21]={1,1,2,6,24,120,720,5040,40320,362880,3628800,39916800,479001600,6227020800,87178291200,1307674368000,20922789888000,355687428096000,6402373705728000,121645100408832000,2432902008176640000};
int main(){
	while(scanf("%d %d",&N,&M)!=EOF){
		printf("%d\n",arr[N]/(arr[N-M]*arr[M]));
	}
	return 0;
}
